Helical spline actuators can transform axial force into rotational torque. Helical spline actuators utilize a combination of shafts, a male shaft that is externally splined and a female shaft that is internally splined. In certain applications, a male shaft can be displaced axially through a female shaft such that the splines engage and the male shaft rotates. Similarly, in certain applications, a female shaft can be rotated in order to cause axial displacement of the male shaft.
Helical spline actuators have been used to actuate ball valves. In certain applications, the output shaft of the actuator can be connected to the valve stem of a ball valve, so that the valve can be moved from a closed position to an open position and vice versa using the actuator. In certain applications, operating torque is generated in the actuator using pressurized fluid (for example, hydraulic fluid) and/or, in the case of single acting spring return actuators, a spring. In certain applications, underwater actuators can also include a gearbox for operation of the valve locally by applying torque to an interface located on the external boundary of the actuator.
Known helical spline actuators suffer from contamination and a relatively short lifespan. There is therefore a need for helical spline actuators that provide reduced contamination and extended lifespan. Further, it is desirable to reduce the size and weight of actuators in order to reduce the space they require and to reduce costs associated with making and using the actuators.